Over the years, there has been an increasing need for high temperature resistant insulation materials within the automotive industry. For example, there is a pressing and continuing demand within the industry for a practical and effective insulation material for the interiors of turbine chambers.
In the past, the materials which have been used for turbine chamber insulation have not been entirely satisfactory. For example, refractory fiber blankets which were hand laid or installed had a limited service life and would delaminate from metal surfaces. Additionally, the blankets were labor intensive to install.
Vacuum formed refractory fiber insulation was also tried. However, it did not form a good bond with the interior surface of the turbine chamber. Furthermore, it suffered from dimensional variations, i.e. the insulation would tend to warp and shift and not fit in the turbine chamber housing.
Somewhat extrudable, refractory fiber containing inorganic bonded insulation material was used in the past. This material was too dense, though, and consequently its thermal conductivity values were too high. The thermal conductivity was also poor because the insulation material would form internal voids during drying. Additionally, the material would not bond well to the aluminum surface of the turbine chamber. Even if the material did form a bond, the insulation would be so rigid that it would deliminate from the metal surface due to variations in thermal expansion.
Therefore, what is needed in the industry is a low density, high temperature resistant insulation material which bonds well to metallic surfaces while being soft enough to remain bonded and reduce the stresses caused by thermal expansion. Other properties such as easy moldability and low shrinkage would also be desirable.